Improved velocity feedback for position control by using a quadratic sliding mode filter

In low-friction position-controlled devices, velocity feedback is required for a proportional-derivative (PD) controller to inject damping into these devices to remove low-frequency vibration. It is known that, in the case of using low resolution sensors, the velocity obtained through numerical differentiation is corrupted by high-frequency noise. Thus, the use of a PD controller results in high-frequency vibration in position control of devices of which sensor resolution and friction are both low. In previous papers, the authors proposed a new quadratic sliding mode filter. In this paper, we present experimental results to show the usefulness of this filter in position control of low-sensor-resolution, low-friction devices to improve velocity feedback.